Air Pressure and Building Envelopes

Abstract

Control of airflow is essential to several important performance aspects of the building system. Air carries moisture which impacts a material’s longterm performance (serviceability) and structural integrity (durability), behavior in fire (smoke spread), indoor air quality (distribution of pollutants and microbial reservoirs) and thermal energy. Typical case studies are presented to illustrate how each of the above characteristics is affected when unintended airflow occurs as a result of poor construction. In some cases, there was simply a lack of understanding of the consequences of ignoring potential leakage paths and the interaction of the mechanical conditioning systems with the building structure. Rehabilitation of a troubled building requires that these interactions be understood. In general, the approach to developing that understanding is not involved.

Evaluating an Exterior Insulation and Finish System for Deep Energy Retrofits

“…To allow for drying of incidental moisture, EIFS assemblies should not contain interior vapor barriers or impermeable interior finishes. "An important exception to this latter requirement is where the drainage plane is also a vapor impermeable air barrier membrane and the interior framing cavities are uninsulated" (Lstiburek, 2007). Drying ability will be enhanced with adequate ventilation through the drainage plane.…”

“…This became a problem, especially because the system usually contained moisturesensitive materials such as gypsum board, oriented strand board, and other wood products. Drained EIFSs include a provision for drainage behind the foam insulation and can be successfully used as an exterior cladding system in most situations (Lstiburek, 2007).…”

A Numerical Study on the Impact of Wind Gust Frequency on Air Exchanges in Buildings with Variable External and Internal Leakages

“…Several studies have presented estimations of the heat load fraction in a building that takes place due to infiltration [2][3][4][5][6][7][8][9][10]. In addition, infiltration has been verified as playing an important role in the internal environment and in the indoor air quality [11][12][13][14]. The heating, ventilation and air conditioning system (HVAC) is also most likely influenced by high infiltration rates, resulting in an offset from the designed inner climate as well as in waste of energy [15].…”

“…In general, openings exposed to turbulent wind can have a large impact on the variation of the internal pressure distribution in a building, affecting the airflow [24,25]. Flows through small cracks (leakages) can potentially cause unacceptable situations from an energy point of view [14]. Turbulence causing wind gustiness is recognized as one major factor that affects infiltration [26].…”

Air infiltration through building envelopes: A review

“…Moisture carried by infiltrating air impacts the long-term performance of the building material and the building’s structural integrity. In addition, leakage airflow impacts the indoor air quality and the distribution of indoor air pollutants (Lstiburek et al, 2002). Air infiltration through a slab-on-grade could even be a route for the transport of detrimental microbes from underlying fill into a building’s indoor space (Rantala and Leivo, 2009).…”